Quasi-Yang-Mills structure for the open bosonic string

Using the description of bosonic open strings by a double rho-form, the ghost-auxiliary field spectrum is derived algebraically, as well as the BRS symmetry, of the free bosonic string theory. A quasi-Yang-Mills structure emerges, where lagrangians and possible anomalies are related to invariant exterior forms of higher rank. The passage from the free case to the interacting one necessitates the understanding of vertex operators defined so as to ensure some geometrical Jacobi-Bianchi identities. (orig.)